
It doesn't ask if it's initial check is OK.
I've updated a number of machines and none have asked unless it sees a problem. If it sees a problem, then you have a problem.
One of my clients thought they were too big for me and when they moved and got all new equipment they went to Verizon for tech support. There was some problem on some of their new Dells and the Verizon guy decided to reinstall Windows XP on them. Instead of asking for the CDs (available) he just shoved in a Verizon corporate license CD.
When the client went to Windows Update (which turned to Microsoft Update a few days later) it saw the corp license, one of the things it looks for, and took him to the enter you number screen. Of course, the number didn't work.
To fix this I did a repair install of Windows XP (so his desktop and registries were retained) using the original Windows XP CD from Dell. It still came up with the check window and wouldn't accep the serial number until a .dll was removed from \\Windows\\System32. The .dll is named legitchk.dll or something like that starting with legit.
[link|http://www.aaxnet.com|AAx]